RN (Relay Node) technology is introduced into LTE (Long Term Evolution) Rel-10 system, with the main purpose of extending the coverage area of eNB (evolved Node B, i.e., base station) cell, wherein the Relay node represents an eNB to the UE (User Equipment) communicated therewith.
In prior art, network architecture diagram of Rel-10 is shown in FIG. 1 after Relay node is introduced.
Introduction of relay node enables three wireless links of Relay-based mobile communication system exist:
Direct link between eNB and macro UE (UE directly served by eNB);
Backhaul link (or named Un link) between eNB and RN;
Access link (or named Uu link) between RN and relay UE (UE served by relay node).
Therefore, such three links shall use orthogonal radio resources in consideration of the signal interference limit of wireless communication.
On the same frequency band, relay node shall not send and receive data simultaneously to avoid self-interference. In LTE Rel-10, relay node may receive downlink backhaul data from donor eNB through the method of MBSFN (Multicast Broadcast Single Frequency Network) subframe, with the receiving scenario diagram shown in FIG. 2.
In an MBSFN subframe, relay node sends PDCCH (Physical Downlink Control Channel) to the served user terminal (R-UE) on one or two OFDM (Orthogonal Frequency Division Multiplexing) symbols. On subsequent OFDM symbols of the MBSFN subframe, the relay node receives the control (named R-PDCCH (Relay-Physical Downlink Control Channel)) and data (named R-PDSCH) from donor eNB.
In the MBSFN subframe configured as downlink backhaul, RN receives R-PDCCH and R-PDSCH (Physical Downlink Shared Channel) sent by donor eNB, eNB starts sending R-PDCCH from the fourth symbol, wherein the DL grant (downlink grant) is sent at the first timeslot and the UL grant (Uplink grant) is sent at the second timeslot. PDSCH (R-PDSCH) of RN can be sent in non-control region of MBSFN by occupying both the first and second slots; or the second slot after DL grant. Multiplex modes of R-PDSCH, R-PDCCH, PDSCH and PDCCH are shown in FIG. 3.
For LTE-Advanced (evolved LTE) system, it is necessary to connect the resources of multiple LTE carriers (also named component carrier) to support the system bandwidth which is wider than LTE system, such as 100 MHz, with two specific modes as below:
Mode I, Aggregate multiple continuous LTE carriers to provide greater transmission bandwidth for LTE-A;
Mode II, Aggregate multiple incontinuous LTE carriers to provide greater transmission bandwidth for LTE-A
FIG. 4 refers to the schematic diagram for the scenario of incontinuous carrier aggregation.
At present, research trend of standardization organization is that carrier aggregation system reaches the following design agreement: design on each carrier keeps in step with LTE Release 8, so as to ensure the terminal of LTE R8 can work normally on each component carrier.
On the other hand, control scheme of PDCCH in LTE-A system mainly refers to the following modes:
Mode I, Independent Scheduling
Each carrier is scheduled independently, and cross-carrier scheduling is not supported. In such case, definition of PDCCH search space of each carrier is consistent with that in LTE R8. The schematic diagram is shown in FIG. 5.
Mode II, Cross-Carrier Scheduling
Other carriers can be scheduled by a carrier, with the schematic diagram as shown in FIG. 6.
In course of implementing the present invention, the inventor finds out there are at least the problems below in prior art:
In Rel-10, the RN is only applied to extending coverage, therefore, only one carrier is supported on Un link, R-PDCCH and PDSCH can only be scheduled on one CC (Component Carrier), while in Relay scheme designed in Rel-10, Un link throughput restricts the system performance, thus becoming the bottleneck to promote the whole network performance. To solve the transmission bottleneck of Un link, one way is to introduce multiple-carrier transmission onto Un link, which is similar to the CA (Carrier aggregation) technology used for high data rate of transmission between the base station in Rel-10 and UE. However, prior art and standard do not support such function.